Land Rover Repair: rear suspension, air leaks, compressor unit

Question
why left side of my lr discII dropes or goes down?And sometimes i here serious of sounds underneth of vehic.like something going on and off.

Answer
The Left Rear is dropping because of air leaks in the SLABS airsprings.  The sounds you hear are probably the compressor unit, either raising the truck or lowering it.  The easiest way to repair is to have a shop with a LR specific diagnostic tool read the codes in the computer.  It does not have to be the dealership if you can find a shop with the right equipment.